Silos inside buildings are often made using a skeleton or a framework in the general shape of a silo, with an exterior shell made of sheets of metal.
The covering of the silo constitutes its interior wall per se, which is in direct contact with the material or the products stored inside. In general, the exterior is attached to the skeleton or framework using conventional methods such as screws, rivets, or the like, while keeping the interior surface as smooth as possible. With this type of construction, it is also necessary for the areas with the greatest exposure to shocks or the areas with wide spaces between portions of the framework to have longitudinal and lateral reinforcements such as girders bracing the structure.
These traditional, prior art designs have numerous drawbacks, particularly from the construction perspective, and involve manual labor when constructing a silo, which is increased even further by the addition of lateral or longitudinal reinforcements.
A silo with a suspended exterior shell is known in the art and described in French Patent Publication No. 2 658 171 in the name of the applicant. This silo consists of a succession of metal forms fastened at their upper edges onto the longitudinal frame elements, and attached in overlapping arrangement at their lower portion in much the same way as roofing tiles or shingles are positioned.
This type of silo eliminates a considerable amount of manual labor and offers quite an improvement over traditional silos. In effect, it is necessary merely to position the metal forms, which have pre-shaped upper edges conforming to the elements of the framework. This is a simple, quick job which can be accomplished by a semi-skilled worker. However, certain aspects of this type of silo can be improved.
One such aspect concerns the edges of the sheets of metal, which have irregular transverse ridges. The products inside the silo, which are in direct contact with these discontinuous areas, may become damaged or even stuck to the ridges, depending upon their nature. The irregularities in the interior silo surface may also mark the stored products if they are made of a deformable, flexible material. This problem often arises during storage of products such as plastic bottles, as a fair number of such bottles emerge from storage with unattractive striations or marks resulting from contact and friction with the edges of the sheet metal. This cosmetic flaw is considered serious enough that silos of this type are not used by certain producers who bottle their products in plastic containers.
The second aspect concerns the possible formation of linear openings between two successive sheets of the metal covering the silo, and in general, the development of frequent leaks in such assemblages, allowing air and dust to enter. For this reason, this type of silo is unsuitable for storing bulk products, particularly food products.